1. Field of the Invention
The present invention relates to a road line recognition apparatus, and more particularly to a road line recognition apparatus which recognizes a road line, following the road line in the shapes of a straight line and a curved line. The road line recognition apparatus recognizes the road line in distinction of whether the road line is continuous line or a broken line, and the recognition apparatus can also recognize a road line branching.
2. Description of Related Art
In recent years, there has been advanced the development of a road recognition apparatus which recognizes a road shape, which is a premise of the improvement of safety, automatic control and the like, by performing the image processing of an imaged image with an on-vehicle stereo camera or an on-vehicle video camera for the improvement of the driving safety of a motorcar or the like, the automatic control of a vehicle, and the like (see, for example, the following Patent Documents 1-3 and the like).
In order to recognize the shape of the road on which a vehicle is running, it is important to recognize the positions of road lines such as a no-passing line marked on a road surface in the front of a own vehicle, division lines by which a roadway is marked off from side strips, and the like. Accordingly, such a road recognition apparatus generally focuses attention on the luminance of the pixels of an imaged image, and is configured to recognize a road line by taking advantage of a significant difference between the luminance of the pixels of a roadway and a road line to extract a pixel portion at which the luminance significantly changes as an edge.
In the present invention, a continuous line and a broken line which are marked on a road surface such as the no-passing line and the division line for marking off the side strip are referred to as road lines, as mentioned above, and the distance between adjacent road lines is referred to as a road width, and further the width of a road line itself is referred to as a road line width.
[Patent Document 1]JP 2001-92970A[Patent Document 2]JP Hei-5-347000A[Patent Document 3]JP 2004-310522A
However, in case of the road recognition apparatus based on the camera information as mentioned above, there is a possibility of mistaking a road mark such as a pedestrian crossing having luminance information similar to that of a road line. In particular, when it is made to be a condition of road line recognition that the interval of a high luminance portion is equivalent to that of a road line width as the road line recognition apparatus described in Patent Document 1, there are some cases where a pedestrian crossing having white line portions thereof each having a width wider than the road line width cannot be detected. Moreover, if the detection width of the high luminance portion in road line recognition is expanded, there are some cases where a pedestrian crossing marked to be thinnish is mistaken as a roadway.
Moreover, in case of the road line recognition apparatus described in Patent Document 1, for example, as shown in FIG. 43A, when white lines indicating road lines are marked so as to cross the front of the course of a driver's vehicle, there are some cases where the marks of the white lines are mistaken as the course of the own vehicle as shown by thick lines in FIG. 43B.
Road recognition, especially the technique for recognizing road lines surely, is a very important technique used as the basis of the automatic control of a vehicle and the information supplement to the driver of the vehicle for realizing various purposes such as an improvement of safeties, such as prevention of collision and rear-end collision, an improvement of the comfort of driving, safety ensuring of a pedestrian crossing a road, and the like, and such a technique is in a technical field the establishment of which is desired strongly.
In such a technology, it is required that it is possible to stably and precisely detect a road line without being especially affected by a complicated road shape such as a sharp curve, dirt on a road surface, rainy weather and the like. Furthermore, it is also desired to precisely grasp and recognize a change of the road width of a road line caused by a road line branching or the like even if the change happens.